Which of the choices is the variance of the sample shown here? 30, 32, 47, 57, 66, 79 with the answers being 205.5, 19.2, 17.6, 371.8, and 309.2

The variance is the average of the squared differences from the mean. The standard deviation is the square root of the variance. So if you ever calculate the standard deviation, the variance is almost the last step of your calculation.

Anyways ... the stddev is 17.6 and the variance is 309.8 (rounded). So really none of the answers match, but 309.2 is pretty close.

First find the mean of these numbers

= 51.833

Then subtract this from each result and square the result. Then work out the average for these squared differences

so we have 30 - 51.833 = - 21.833 and this squared = 476.68

now do the same for the other 6 numbers and total up all the squares

divide this total by 7 will give you the variance